478 WILBURT C. DAVISON 



than incubated at 37°C. and the degree of lysis was noted mac- 

 roscopically at various intervals for seventy-two hours. 



Inasmuch as it had been shown (Davison, 1922a) that agar 

 subcultures of organisms which have been attacked by bac- 

 teriolysants contain "sensitive," "moth eaten" colonies, the 

 presence of such colonies in subcultures was used as confirmatory 

 evidence of the occurrence of lysis. However, subcultures of 

 some bacterial suspensions which had apparently been lysed by 

 a filtrate contained nothing but regular colonies, so that their 

 absence does not necessarily mean that lysis had not occurred. 



Frequently when normal dysentery bacilli, which had been 

 incubated with a bacteriolysant, were subcultured in peptone 

 water these subcultures failed to grow, although agar subcultures 

 made at the same time, contained a number of "sensitive" and 

 regular colonies. It is possible that there was sufficient bac- 

 teriolysant carried over in the subculture loop to inhibit growth 

 in a fluid medium while on agar, this small amount was lost in 

 streaking across the plate. 



The amount of bacteriolysant added to a culture of dysentery 

 bacilli, apparently does not have a quantitative effect on the 

 percentage of "sensitive" colonies which are found in agar sub- 

 cultures of these baciUi, i.e., subcultures of peptone water cul- 

 tures of dysentery bacilU some of which had been incubated with 

 0.5 cc. and others with 0.1 cc. of a bacteriolysant frequently had 

 the same percentage of "sensitive" colonies. 



In several instances I have confirmed these determination 

 of lysis by counting the organisms (plate counts) before and 

 after the action of a bacteriolysant and have found the reduction 

 of viable organisms to be proportional to the degree of lysis, i.e., ■ 

 a culture which contained 100,000,000 Flexner baciUi per cubic 

 centimeter at the commencement of the experiment, and which 

 after twenty-fouj hours' contact with a filtrate was apparently 

 completely lysed, contained two viable organisms per cubic centi- 

 meter (table 2). It is, of course, impossible to state whether 

 this reduction in the number of viable organisms is altogether the 

 result of the bactericidal action of the bacteriolysant or whether 

 inhibition does not also play a part. Several cultures which 



